1. Technical Field
The present invention relates to a flow sensor which is suitable for direct measurement of mass flows, preferably including air or other gases.
2. Background Information
Typically, flow sensors are used in applications in which a defined mass of air or gas per unit of time must be supplied. A typical application is in the intake conduit of internal combustion engines in motor vehicles, for example. The flow sensors used there are placed directly in the flow to be measured so that the flow to be measured circulates around the flow sensors. Known flow sensors are embodied as hot-film sensors and include various sensor windings and optionally heater structures, which are applied via conventional thin-film technology to thin glass or ceramic substrates.
In use, however, such flow sensors prove problematic. First, because of the thin substrates employed, the resultant mechanical sensitivity is high. Second, the flow sensors and substrates, because during production they are cut apart by a sawing process, have edges on which dirt can be deposited in operation, leading to incorrect measurements.
For solving these problems, a flow sensor is proposed in German patent disclosure DE 10 2005 016 122 A1 in which a sensor chip is surrounded, either entirely or partially, by a plastic component. The plastic component can also be embodied in certain regions as a leading edge. In this way, the aforementioned disadvantages in terms of mechanical stability and soiling or contamination are avoided. However, for certain type of sensor elements, the flow to be measured does not circulate around the actual sensor element in an ideal manner.